The production of cinematographic films with stereo sound tracks has been known for some time and, more recently, stereo sound tracks have been produced for video recordings. In order to enhance the effect of sounds emanating from different directions, the stereo principle has been extended by the provision of six separate audio channels, consisting of a front left, front right, front centre, rear left, rear right and a low frequency channel, often referred to as a boom channel. Thus, with such an arrangement, it is possible to position a sound anywhere within a two-dimensional plane, such that the sound sources appear to surround the audience.
The position of a sound source in the six channel system is determined by the contribution made by signals derived from a recorded track for that respective source, to each of the five spatially displaced channels. The allocation of a contribution to these channels is determined during the mixing process, in which many input tracks are combined and distributed, in varying amounts, to said five output channels. Conventionally, the mixing of these channels has been done under the manual control of an operator, in response to the adjustment of manual sliders or manual joysticks etc. Thus, in known systems, an operator is able to control the contribution of the originating sound to each of the channels. Or, considered from the view point of the originating sound source, an operator is in a position to control the gain of each of the five channels independently, thereby enabling said operator to simulate the positioning of the sound source within the sound-plane of the auditorium.
A problem with known systems, which are capable of operating in a professional environment, is that a significant amount of skill is required on the part of an operator, in order to position a sound correctly within the listening plane. Although an operator has complete control as to the extent to which gain is controlled for each of the channels, he has very little guidance as to how this control should actually be exercised. Furthermore, this problem becomes particularly acute if a modification is required so as to reposition a sound source, in that it may not be at all apparent to an operator as to what modifications to the gains are required to effect the re-positioning of the sound source as required.
Computerised systems have been proposed which allow the position of a sound source to be defined via a graphical user interface. However, a problem with procedural software approaches is that the processing requirements are substantial if a plurality of channels, each conveying digitally encoded audio information, are to be manipulated simultaneously.
It is an object of the present invention to provide an improved method and apparatus for simulating the position of the sound in space.